Oil Pressure

[LAW75]

Hi there fellow travelers. Have a question re my AH 3000 Mk III BJ8 Phase 2 oil pressure. Just had all the gaskets (ALL) replaced, including the relevant oil seals. My best recollection is prior to this, my oil pressure was about 15 at idle and 50-55 when warm and at about 40mph+. Now my pressure is at 15ish at idle and only 40 at 40mph+. The mechanic that replaced all the gaskets and oil seals said that the "40" oil pressure read is "not a big issue" and should not harm the engine nor effect performance. I know the books say the pressure at warm and accelerating speeds should be about 55ish. Is there any agreement with the mechanic? Or should I have concern?
PS. 1. I have an after market oil filter, 2. Checked oil level, 3. using "correct" oil weight, 4. no leaks of any concern, 5. car was restored about 10K miles ago.
Any insight, suggestions or directions would be greatly appreciated.
Thanks

 

[roscoe]

Your mention of the seals being recently changed is probably a red herring in that changing gaskets and seals would not normally alter oil pressure. 40 psi at cruise is a bit low for a relatively recent rebuild but not likley to do any harm if you aren't driving it hard. Do remember that the oil pressure is adjustable, within limits, by adding ( to increase) or removing ( to decrease) small shims or washers from behind the spring on the oil pressure relief valve on the engine block. To bump it up 5psi or so by adding shim thickness is simply done by trial and error.

 

[LAW75]

Thank you much Roscoe. Any idea what increase one (say 1/8" thick) washer would increase it by?

 

[roscoe]

The first thing to do might just be to remove the cap, spring and plunger. See if there are any washers(shims) already in place, clean the bore, the seat and the plunger. If the plunger is not seating cleanly it could cause lower oil pressure. Sometimes just cleaning everything up is the fix. A small amount of overhaul debris on the seat is possible. If that changes nothing adding an eigth inch might be a bit much. Try half that and see. You'll likley need a magnet to remove the plunger. Do not attempt to clean the seat with anything that might get stuck or leave debris. The overhauler should have lapped the seat and plunger together when the block was stripped and before cleaning but it is sometimes overlooked. I always check the plunger and seat seal with some machinists blue dye to see if there is a good concentric seal between the two. Your mechaanic should know how to do that if you do not.

 

[LAW75]

Roscoe, wow! You da (politically correct) "significant person".